The present invention pertains to a plug-in adapter for gas sampling for a gas sensor.
A device for gas sampling for a gas analyzer has become known from GB 2 105 849 A. The gas is suctioned by means of a pump from the ambient atmosphere and is then fed in a serial sequence to various gas sensors, with which individual gas components can be detected. In this case, the pump works in the so-called pressure operation, in which the gas is suctioned via a flow channel from the ambient atmosphere and then arrives at the sensors behind the pump. The measured gas flows out to the environment via a discharge line. The arrangement of the sensors on the pressure side of the pump is therefore selected because the pressure difference relative to the environment is usually lower on the pressure side of the pump.
However, in some gases, and especially at low gas concentrations, there is the danger that the measured gas component in the pump, which is usually designed as a diaphragm pump, is adsorbed. This effect occurs, e.g., in chlorine and volatile hydrocarbons. In order to minimize the contact with adsorbing materials, such as, e.g., the pump diaphragm, the sensor in these cases is arranged in front of the pump, i.e., on the suction side.
Sensors for the detection of gas components are usually installed in the so-called measuring heads, in which the measuring signals are processed, in order to then display them either on the measuring head itself or on a central evaluation unit. The processing of the measuring signals here includes a calibration and adaptation to the gas type and measuring range. Such measuring heads, which also contain the measured gas pump internally, are usually suitable for accommodating different sensors, which are inserted into the measuring head. Thus, it seems that, depending on the gas component to be-detected, sensors must be arranged either in the, suction area or the pressure area of the measured gas pump.
The object of the present invention: is to improve a device for gas analysis in such a way that sensors can be arranged in a simple manner on the suction or pressure side of the measured gas pump.
According to the invention, a device is provided for gas analysis with a sensor, a measured gas pump and with a plug-in adapter that can be connected with the measured gas pump and the sensor. The plug-in adapter has a first measuring channel that is in flow connection with a gas-sensitive surface of the sensor. The said plug-in adapter can be connected with the measured gas pump in two positions in such a way that a connecting branch of the first measuring channel is connected in a first position of the said plug-in adapter on the pressure side and in a second position on the suction side of the said measured gas pump.
The advantage of the present invention lies essentially in the fact that a plug-in, adapter, which has a first measuring channel that is in a flow connection with the gas-sensitive surface of the sensor, can be put on the measuring head containing the measured gas pump in two positions. As a result the sensor is located either on the suction side or pressure side of the measured gas pump, depending on the position of the plug-in adapter. The plug-in adapter is preferably designed as an injection molding part, so that all necessary connections can be connected directly with the basic body.
Advantageously, the sensor and the measured gas pump are accommodated in a measuring head, in which case plug sockets for connecting with the suction side and pressure side, as well as the gas-sensitive surface of the sensor, are arranged on a connection surface of the measuring head, which is turned towards the plug-in adapter.
The plug sockets of the measured gas pump and the sensor are positioned on the connection surface of the measuring head in such a way that the plug-in adapter, adapting to any sudden change, can be placed on the measuring head in the two positions.
Advantageously, the plug-in adapter has a measuring channel that can be connected with that plug socket of the measured gas pump that is not occupied -by the first measuring channel. By means of the measuring channels, which are guided on the outside of the plug-in adapter, it is possible to connect hoses to the plug-in adapter, so that a gas sample can also be suctioned and evaluated from a site lying at a remote distance.
It is especially advantageous to provide a switching element on the measuring head that determines the position of the plug-in adapter. The switching element may be designed, e.g., as a microswitch, which is closed in a certain position of the plug-in adapter and which remains in the opened position in another position of the plug-in adapter. This microswitch is connected with an evaluation and control unit of the measuring head, so that it is recognized in the measuring head whether the pertinent type of operation, such as suction operation or pressure operation, is also set for the sensor used.